This invention relates to a method of manufacturing a superconducting oxide wafer. It especially, relates to the method of forming a plural system oxide single crystal thin film having superconducting characteristic on a crystal substrate.
The electric resistance of a metal decreases as a temperature falls. Even when, the temperature nears an absolute zero point, an ordinary metal has a finite electric resistance. However, it has been confirmed that the electric resistance of some metals vanishes suddenly at some temperature. A complete conductive state appearing in some metals at a critical temperature Tc or less is called a superconducting state, and this phenomenon is called the superconductivity phenomenon.
Recently, high temperature superconducting objects presenting the superconductivity phenomenon at the high temperature of the temperature of liquid nitrogen have been discovered. Especially, plural system oxide superconducting objects having the Perovstkite structure are of interest. Typical plural system oxide superconducting objects are the YBa.sub.2 Cu.sub.3 O.sub.7-.delta. and the (La, Ba).sub.2 CuO.sub.4-y, etc.
These plural system oxide superconducting objects are manufactured by sintering, evaporating or sputtering processes, etc. It is a key technique that the superconducting objects be obtained as a thin film made by a single crystal to be widely applicable to new devices using the superconducting objects.
It has been reported to form the superconducting single crystal film on the substrate by melting the raw materials at 1000.degree. C. or more and to cool gradually. However, the thin film was experimentally formed only as the very minute pieces. Large superconducting thin film necessary to be applicable to practical devices have not heretofore been manufactured by practical processes having reproducibility and mass-productivity. The realization of a large oxide superconducting single crystal thin film in which the superconducting transposition temperature is high, the operating characteristic is stable and the critical current is also large is strongly desired.